In the MFO Rise of Nations Forum someone was arguing that Starcraft is the best RTS game ever. I disagreed. Starcraft is one of the best games ever made, but IMO, there are certain things missing from Starcraft that are in other games.

Unit experience (units can level up, like Red Alert 2 and Kohan)

Unit facing (tactical maneuver is important, like RON and Kohan)

Random maps (variety, like all the other games)

Logistics (some representation of supply requirements, like RON and Kohan)